quiz 1 and quiz 2

Middle cerebral artery (The trainer is experiencing fairly severe motor and sensory deficits. Since the middle cerebral artery supplies blood to the lateral cerebral hemispheres including most of the primary motor cortex and the primary somatosensory cortex, it is the likely culprit here. Remember if this was his dominant hemisphere, he would likely also suffer drastic language deficits as well.)

A 62 year old, lizard trainer, while berating a badly behaving basilisk, had the sudden onset of a headache and weakness of his left arm and leg. He looked in a mirror and noted that the left side of his face had begun to droop. He complained that the left side of his body felt "numb" and he was found to have diminished touch and position sense on the left. The most likely cause of this episode is an occlusion of which artery?

cerebral aqueduct (Cerebrospinal fluid flows from the 3rd ventricle, through the midbrain via the cerebral aqueduct, and into the 4th ventricle.)

How does cerebrospinal fluid flow into the 4th ventricle?

Arachnoid granulations (Cerebrospinal fluid is reabsorbed into the blood of the dural venous sinuses via the arachnoid granulations.)

How does cerebrospinal leave the subarachnoid space?

sodium channel inactivation (After the peak of depolarization, the sodium channels become inactivated. This prevents action potential from propagating in the reverse direction. This is the absolute refractory period.)

In the normal axon, why is reverse propagation of the action potential is not possible?

middle cerebral artery (The middle cerebral artery supplies blood to the lateral portion of the cerebral hemisphere. This is an area where most of the primary motor cortex and primary somatosensory cortex is located. As a result, the loss of blood flow though this artery would cause major sensory and motor deficits. However, there may be some sparing of motor usage and sensation in the lower extremity because most of this area of the primary motor cortex and primary somatosensory cortex is supplied by the anterior cerebral artery.)

Major sensory and motor deficits that are particularly prominent in the upper extremity would result from a blockage of which of the following arteries?

Hyperpolarize (Opening a chloride channel will allow negatively charged chloride ions to flow into the cell, making the inside more negative.)

Opening a ligand-gated chloride channel will cause the resting membrane potential to do which of the following?

anterior inferior cerebellar artery (The anterior inferior cerebellar artery is the second branch of the vertebral/basilar artery system. As its name implies, it supplies the anteroinferior portion of the cerebellum. On its way to that area, it also gives off perforating branches that supply the caudal (inferior) pons.)

The caudal (inferior) pons receives much of its blood supply from what artery?

frontal from parietal (The central sulcus runs perpendicular to the lateral sulcus on the lateral surface of the cerebral hemisphere, separating the frontal and parietal lobes.)

The central sulcus separates which lobes?

anterior cerebral artery (From chapter 3 you should remember that the cingulate gyrus is on the medial surface of the cerebral hemisphere, just superior to the corpus callosum. The anterior cerebral artery supplies blood to the medial portions of the frontal and parietal lobes, as well as the corpus callosum.)

The cingulate gyrus receives most of its arterial blood supply form what artery?

primary motor cortex (The primary motor cortex is located on the precentral gyrus adjacent to the premotor area.)

What area is located in/on the precentral gyrus?

sodium and potassium will flow through the same channel (A single cation channel opens allowing sodium ions to flow into the cell and potassium ions to flow out simultaneously. Since the flow of sodium is much greater, more positive charges will enter the cell and it will become depolarized.)

What happens when an excitatory postsynaptic potential (EPSP) is being generated on a dendritic membrane?

voltage-gated sodium channel (During depolarization voltage-gated sodium channels open and allow sodium to rush into the cell. This leads to a spike in membrane potential.)

What is the main ion channel responsible for the depolarization phase of an action potential?

Voltage-gated calcium channel (Depolarization of the membrane of the presynaptic axonal terminal leads to opening of voltage-gated calcium channels. This influx of calcium into the neuron terminal, combined with the release of calcium from intracellular stores, triggers the movement of synaptic vesicles toward a release site in the membrane. Synaptic vesicles fuse with the membrane and release neurotransmitter into the synaptic cleft.)

What is the main ion channel responsible for the release of neurotransmitter from the axonal terminal?

voltage-gated potassium channel (Following the spike in depolarization, voltage-gated potassium channels open. This allows potassium to escape from the cell carrying positive charge with it. This brings the membrane potential back toward resting levels.)

What is the main ion channel responsible for the repolarization phase of an action potential?

Thalamus (The thalamus serves as a switchboard for information going to the cerebral hemispheres. It decides which information needs to be sent to which cerebral areas.)

Which area is a major relay center for information going to the cerebral hemispheres?

myelinated, large diameter (The larger the diameter of the axon, the faster the conduction velocity will be. Myelination also increases conduction velocity. Therefore, a large, myelinated axon would have the fastest conduction velocity.)

Which axon type would have the highest action potential conduction velocity?

Oligodendrocytes (Oligodendrocytes myelinate axons in the CNS while Schwann cells do it in the PNS. Remember oligodendrocytes can myelinate multiple axons while Schwann cells can only myelinate one axon.)

Which cells create the myelin sheath of axons in the central nervous system?

Epyndimal Cells (Ependymal cells line the ventricles and form the blood-CSF barrier, which is a part of the blood-brain barrier. Astrocytes play a major role in making up the remainder of the blood-brain barrier.)

Which cells form the blood-CSF barrier which is part of the blood-brain barrier?

GABA (GABA usually causes fast IPSPs in the brain while glycine does the same in the spinal cord.)

Which neurotransmitter usually causes fast inhibitory postsynaptic potentials (IPSPs) in the brain?

Superior sagittal, straight, and occipital sinuses (The superior sagittal, straight, and occipital sinuses all drain blood into the confluence of sinuses. Blood then leaves the confluence of sinuses through the two transverse sinuses.)

Which of the following drain blood into the confluence of sinuses?